Subversion Repositories simple_fm_receiver

-- $Id: addacc.vhdl,v 1.2 2005-02-21 06:54:22 arif_endro Exp $

-------------------------------------------------------------------------------

-- Title       : Accumulator and Adder

-- Project     : FM Receiver 

-------------------------------------------------------------------------------

-- File        : addacc.vhdl

-- Author      : "Arif E. Nugroho" <arif_endro@yahoo.com>

-- Created     : 2004/10/25

-- Last update : 

-- Simulators  : 

-- Synthesizers: 

-- Target      : 

-------------------------------------------------------------------------------

-- Description : Accumulator used in NCO of PLL in FM Receiver

-------------------------------------------------------------------------------

-- Copyright (C) 2004 Arif E. Nugroho

-- This VHDL design file is an open design; you can redistribute it and/or

-- modify it and/or implement it after contacting the author

-------------------------------------------------------------------------------

-------------------------------------------------------------------------------

-- 

--      THIS SOURCE FILE MAY BE USED AND DISTRIBUTED WITHOUT RESTRICTION

-- PROVIDED THAT THIS COPYRIGHT STATEMENT IS NOT REMOVED FROM THE FILE AND THAT

-- ANY DERIVATIVE WORK CONTAINS THE ORIGINAL COPYRIGHT NOTICE AND THE

-- ASSOCIATED DISCLAIMER.

-- 

-------------------------------------------------------------------------------

-- 

--      THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR

-- IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

-- MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO

-- EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

-- SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

-- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;

-- OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

-- WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

-- OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

-- ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-- 

-------------------------------------------------------------------------------

library IEEE;

use IEEE.STD_LOGIC_1164.all;

use IEEE.STD_LOGIC_arith.all;

entity addacc is

   port (

    clock  : in  bit;

    acc    : in  bit_vector (17 downto 0);

    result : out bit_vector (17 downto 0);

    offset : in  bit_vector (17 downto 0)

    );

end addacc;

architecture structural of addacc is

   component adder_18bit

      port (

      addend_18bit   : in  bit_vector (17 downto 0);

      augend_18bit   : in  bit_vector (17 downto 0);

      adder18_output : out bit_vector (17 downto 0)

      );

   end component;

signal result_adder01     : bit_vector (17 downto 0);

signal result_adder02     : bit_vector (17 downto 0);

signal result_adder02_reg : bit_vector (17 downto 0);

begin

adder01 : adder_18bit

  port map (

  addend_18bit     => offset,

  augend_18bit     => acc,

  adder18_output   => result_adder01

  );

adder02 : adder_18bit

  port map (

  addend_18bit     => result_adder01,

  augend_18bit     => result_adder02_reg,

  adder18_output   => result_adder02

  );

  process (clock)

  begin

          if ((clock = '1') and clock'event) then

                  result_adder02_reg <= result_adder02;

                  result <= result_adder02;

          end if;

  end process;

end structural;